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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"
  1. GRB 250127A: SVOM detection of a long burst
  2. GRB 250126A: CALET Gamma-Ray Burst Monitor detection
  3. EP250125A: Non-detection from Fermi-GBM Observations
  4. GRB 250126A: MAXI/GSC detection
  5. EP250108a / SN 2025kg: Refined Analysis of EP-WXT Detection
  6. GRB 250126A: BALROG localization (Fermi Trigger 759560335 / GRB 250126208)
  7. GRB 250126A: Fermi GBM Final Real-time Localization
  8. GECAM-A detection of a bright burst from SGR 1E1841-045
  9. GRB 250118A: Fermi GBM Observation
  10. EP250125a: Optical upper limit with Kinder observations
  11. EP250125a: REM optical counterpart detection
  12. GRB 250119C: Fermi GBM Observation
  13. EP250125a: Swift/XRT detection of a fading counterpart
  14. EP250125a: a new X-ray transient detected by Einstein Probe
  15. EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89
  16. The EP-WXT trigger 01709130758 is a false trigger
  17. The EP-WXT trigger 01709130758 is a false trigger
  18. Konus-Wind detection of a bright burst from SGR 1E1841-045 on 2025 January 23
  19. GRB 250121A: Swift/BAT-GUANO localization skymap of a burst
  20. IPN triangulation of a bright burst from SGR 1E1841-045
  21. GRB 250121A: CALET Gamma-Ray Burst Monitor detection
  22. EP250108a: AbAO, CMO and Terskol optical upper limits
  23. Konus-Wind detection of GRB 250118B
  24. GRB 250121A: Fermi GBM Observation
  25. IPN triangulation of GRB 250118B
  26. Konus-Wind detection of GRB 250119B
  27. IPN triangulation of GRB 250119B
  28. GRB 250122A: Fermi GBM Final Real-time Localization
  29. Improved IPN triangulation of GRB 250107C
  30. GRB 250114A: Swift-BAT refined analysis
  31. GRB 250121A: INTEGRAL/SPI-ACS detection
  32. GRB 250121A: Fermi-LAT detection
  33. LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
  34. GRB 250119C: Swift/BAT-GUANO localization skymap of a short burst
  35. GRB 250119B: Swift/BAT-GUANO localization skymap of a long burst
  36. GRB 250121A: Fermi GBM Final Real-time Localization
  37. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  38. GRB 250118A: Swift/BAT-GUANO localization skymap of a short burst
  39. GRB 250119B: Fermi GBM Observation
  40. EP250108a/AT2025kg: 1.3m DFOT Optical observations
  41. Konus-Wind detection of GRB 250117A
  42. IPN triangulation of GRB 250117A (short)
  43. ATCA detection of possible radio counterpart to GRB 250114A
  44. EP250108a / SN2025kg: Non-detection from ATCA radio follow-up observations
  45. GRB 250119B: INTEGRAL/SPI-ACS detection
  46. LIGO/Virgo/KAGRA S250119cv: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  47. EP 250108A: Late-time optical observation by LCO
  48. GRB 250117A: SVOM/GRM observation of a short burst
  49. LIGO/Virgo/KAGRA S250105bn: 1 counterpart neutrino candidate event from an IceCube neutrino search
  50. LIGO/Virgo/KAGRA S250119cv: Updated NED Galaxies in the Localization Volume
  51. LIGO/Virgo/KAGRA S250119cv: Updated Sky localization and EM Bright Classification
  52. GRB 250119C: Fermi GBM Final Real-time Localization
  53. LIGO/Virgo/KAGRA S250119cv: NED Galaxies in the Localization Volume
  54. GRB 250117A: Swift/BAT-GUANO localization skymap of a short burst
  55. EP250108a / SN2025kg: Gemini GMOS-S confirmation of an associated broad-lined SN Ic
  56. LIGO/Virgo/KAGRA S250119cv: Identification of a GW compact binary merger candidate
  57. LIGO/Virgo/KAGRA S250119ag: Updated Sky localization
  58. EP250108a/AT 2025kg: NOT spectroscopy in agreement with SN Ic-BL
  59. EP250108a / AT 2025kg: the kangaroo is hopping, evidence for optical rebrightening
  60. GRB 250117A: GECAM observation of a short burst
  61. LIGO/Virgo/KAGRA S250118dp: Updated Sky localization
  62. GRB 250119B: BALROG localization (Fermi Trigger 758968026 / GRB 250119352)
  63. GRB 250119B: Fermi GBM Final Real-time Localization
  64. LIGO/Virgo/KAGRA S250119ag: Identification of a GW compact binary merger candidate
  65. GRB 250119A: Fermi GBM Final Real-time Localization
  66. GRB 250118A: Fermi GBM Final Real-time Localization
  67. LIGO/Virgo/KAGRA S250118dp: Identification of a GW compact binary merger candidate
  68. LIGO/Virgo/KAGRA S250118t: Updated Sky localization
  69. LIGO/Virgo/KAGRA S250118az: Identification of a GW compact binary merger candidate
  70. EP250108a / AT2025kg: GMG Optical Observations
  71. LIGO/Virgo/KAGRA S250118t: Identification of a GW compact binary merger candidate
  72. EP250108a / AT2025kg: VLA radio upper limit
  73. Fermi Gamma-ray Burst Monitor trigger 758829338/250117747 is not a GRB
  74. Konus-Wind detection of GRB 250116A
  75. GRB 250116A: GECAM-B detection of a long burst
  76. GRB 241217A / EP241217B: radio detection with the VLA
  77. GRB 250116A: INTEGRAL/SPI-ACS and PICsIT detection
  78. Swift Trigger 1282245 is not a GRB
  79. GRB 250116A: Fermi-LAT detection
  80. GRB 250116A: Fermi GBM Observation of an Extremely Interesting Burst
  81. GRB 250114B: Swift-XRT afterglow detection
  82. GRB 250114B: SVOM/VT upper limit
  83. Fermi Gamma-ray Burst Monitor trigger 758659047/250115776 is not a GRB
  84. EP250108a: MeerKAT radio upper limit
  85. LIGO/Virgo/KAGRA S250114ax: Updated NED Galaxies in the Localization Volume
  86. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
  87. LIGO/Virgo/KAGRA S250114ax: Updated Sky localization
  88. Konus-Wind detection of GRB 250113A
  89. IPN triangulation of GRB 250113A
  90. GRB 250114B: Liverpool Telescope optical upper limit
  91. LIGO/Virgo/KAGRA S250114ax: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  92. GRB 250114B : MITSuME Akeno optical afterglow candidate detection
  93. GRB 250114B: Swift-XRT observations
  94. GRB 250114A: LCO optical counterpart detection.
  95. GRB 250114B: OHP/T193 optical upper limit
  96. GRB 250114A: GRANDMA/TAROT optical afterglow detection
  97. GRB 250114A: Swift-XRT refined Analysis
  98. Integral GRB250114.55: Global MASTER-Net observations report
  99. GRB 250114A: LCOGT optical afterglow i-band detection
  100. GRB 250114B : GIT optical upper limit

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